Population and reproductive biology of two caprellid species (Crustacea: Amphipoda) associated to Sargassum cymosum (Phaeophyta: Fucales) on the southeast coast of Brazil

Abstract Caprellid amphipods are common crustaceans at Sargassum beds of southeastern Brazil and constitute an important link between primary producers and marine consumers. The goal of this study is to evaluate population and reproductive biology of two caprellid species: Paracaprella tenuis Mayer, 1903 and Pseudaeginella montoucheti Quitete, 1971. Sargassum cymosum Agardh, 1820 samples were collected monthly between October 2010 and September 2011 in a rock shore in southeastern Brazil. The caprellids were identified, counted, measured and classified as males, immature females, sexually mature females, ovigerous females and juveniles. Eggs were counted and measured. Higher densities of P. tenuis and P. montoucheti were found mainly in winter and lower densities in fall and summer. Density variation is probably related to organic matter supply and substrate availability. Both species showed continuous reproduction with reproductive peaks. Pseudaeginella montoucheti larger egg volume indicates a longer incubation period. The egg volume was directly related to female size. The number of eggs was weakly related to female size, indicating that fecundity may be driven by other factors, such as the physiological conditions. Sex ratio deviated for males suggests a higher longevity of males. The present study highlighted important data of two caprellids species that occur in algal beds of different regions.

摘要 麦秆虫类钩虾（Caprellid amphipods）是巴西东南部马尾藻床（Sargassum beds）的常见甲壳类动物，是初级生产者与海洋消费者之间的关键营养联结环节。本研究旨在评估两种麦秆虫类钩虾的种群与生殖生物学特征：纤细副麦秆虫（Paracaprella tenuis Mayer, 1903）以及蒙图切伪爱根虫（Pseudaeginella montoucheti Quitete, 1971）。研究于2010年10月至2011年9月期间，在巴西东南部的岩岸海域每月采集膜叶马尾藻（Sargassum cymosum Agardh, 1820）样本。研究人员对采集到的麦秆虫类钩虾进行物种鉴定、计数、体长测量，并将其划分为雄性、未成熟雌性、性成熟雌性、抱卵雌性以及幼体五类，同时对卵粒进行计数与体积测量。结果显示，纤细副麦秆虫与蒙图切伪爱根虫的种群密度均以冬季为最高，秋季与夏季密度较低，其密度波动可能与有机质供给量以及基质可获得性相关。两种麦秆虫均呈现连续生殖模式，并存在生殖高峰时段；蒙图切伪爱根虫的卵粒体积更大，提示其胚胎孵化周期更长。卵粒体积与雌性个体体长呈显著正相关，而抱卵量仅与雌性体长呈弱相关，提示其繁殖力可能受生理状态等其他因素调控。种群性比偏向雄性，提示雄性个体具有更长的寿命。本研究为分布于不同海域藻床的两种麦秆虫类钩虾提供了重要的基础生物学数据。